Diamonds and graphite are known as substances composed of carbon alone. Recently, a spherical cluster molecule that consists of 60 carbon atoms was found, and physical properties and applications thereof have been studied. This molecule is referred to as “fullerene” and has a soccer-ball-like shape. Furthermore, it has been reported that an aggregate of fullerene molecules is a face-centered cubic lattice and a substance having superconductive characteristics can be obtained by doping it with various elements.
A method of adding isopropyl alcohol to a toluene solution including fullerene dissolved therein has been reported as a method for obtaining fullerene crystals (K. Miyazawa, et al., J. Mater. Res., Vol. 17, No. 1, 83 (2002)). This reference describes that needle single crystals of fullerene having a diameter of 200 nm to 2 μm and a length of 0.15 mm to 5 mm are obtained. This method, however, had problems in that only a small amount of fullerene crystals deposit and the yield of the fullerene crystals is low.
Furthermore, JP05(1993)-124894A discloses, as a method of obtaining large single crystals of fullerene, a method of depositing fullerene crystals on a single crystal substrate of rubidium bromide, potassium iodide, or rubidium iodide by a vacuum deposition method. This method, however, requires a vacuum deposition apparatus having a vacuum degree of about 1.3 Pa×10−4 Pa and also requires a single crystal substrate to be used for growing fullerene single crystals. Accordingly, the method includes complicated processes, which results in high costs for manufacturing fullerene single crystals.
JP10(1998)-001306A discloses, as a method of obtaining particulate crystals of fullerene, a method for producing fullerene polymers (for instance, crystals whose diameter is around 50 nm) by adding a poor solvent of fullerene (for example, ethanol) to a solution including fullerene dissolved therein (for instance, a benzene solution of C60 fullerene). The particulate crystals obtained by this method, however, have particle sizes as small as several nanometers and therefore are not suitable as materials to be subjected to observations and evaluations of fullerene crystals as well as surface reactions.
Moreover, a method of adding isopropyl alcohol to a toluene solution containing fullerene dissolved therein is disclosed as a method of obtaining needle crystals of fullerene (Kun-ichi MIYAZAWA, Heat Treatment, Vol. 42, No. 2, p. 81). This method, however, does not allow crystals to be obtained with a high yield.